Thin film transistor, method of manufacturing the same and flat panel display having the thin film transistor

ABSTRACT

A thin film transistor includes: a gate electrode; source and drain electrodes insulated from the gate electrode; an organic semiconductor layer that is insulated from the gate electrode and electrically connected to the source and drain electrodes; an insulating layer that insulates the gate electrode from the source and drain electrodes or the organic semiconductor layer; a hydrophobic layer which covers the source and drain electrodes or insulating layer and has an opening that defines a region corresponding to the organic semiconductor layer; and a hydrophilic layer formed in the opening of the hydrophobic layer, wherein the organic semiconductor layer is formed on the hydrophilic layer. The thin film transistor includes the organic semiconductor layer having a highly precise pattern that is formed without an additional patterning process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.2005-99614, filed on Oct. 21, 2005, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention relate to a thin film transistor (TFT),a method of manufacturing the same, and a flat panel display having theTFT, and more particularly, to a TFT including an organic semiconductorlayer that is spontaneously formed on a hydrophilic layer and that isnot formed in a hydrophobic region surrounding the hydrophilic layer.Aspects of the present invention further include a method ofmanufacturing the TFT and a flat panel display having the TFT. Since theTFT includes the organic semiconductor layer having a highly precisepattern that is formed without an additional patterning process of theorganic semiconductor layer, the manufacturing cost and time are low. Inaddition, the TFT has improved electric properties.

2. Description of the Related Art

Thin film transistors (TFTs), which are used in flat panel displays,such as liquid crystalline display devices (LCD), organic light-emittingdisplay devices, inorganic light-emitting display devices, and the like,are used as switching devices for controlling pixel operations and asdriving devices for operating pixels.

TFTs include a semiconductor layer including source/drain regions and achannel region interposed between the source region and drain region, agate electrode insulated from the semiconductor layer and located in aregion corresponding to the channel region, and source and drainelectrodes respectively contacting the source and drain regions.

Organic TFTs include an organic semiconductor layer composed of anorganic semiconductor material. Organic TFTs can be manufactured at lowtemperatures, and thus, a plastic substrate can be used. Due to theseadvantages of organic TFTs, recent research into organic TFTs has beenperformed. For example, Korean Patent Publication No. 2004-0012212discloses an organic TFT.

When an organic TFT is manufactured, patterning of the organicsemiconductor layer is necessary. However, when the organicsemiconductor layer is patterned, material of the organic semiconductorlayer can be degraded, and film layers located under the organicsemiconductor layer can be damaged, and thus, the electric properties ofthe organic TFT can deteriorate. Further, additional patterning of theorganic semiconductor layer can increase the manufacturing cost and timeconsumption. Therefore, an improvement regarding these issues isrequired.

SUMMARY OF THE INVENTION

Aspects of the present invention provide a thin film transistor (TFT)including an organic semiconductor layer that is formed on a hydrophiliclayer, a method of manufacturing the same and a flat panel displayhaving the TFT.

According to an aspect of the present invention, there is provided a TFTincluding: a gate electrode; source and drain electrodes insulated fromthe gate electrode; an organic semiconductor layer insulated from thegate electrode; an organic semiconductor layer that is insulated fromthe gate electrode and electrically connected to the source and drainelectrodes; an insulating layer that insulates the gate electrode fromthe source and drain electrodes or the organic semiconductor layer; ahydrophobic layer having an opening that defines a region correspondingto the organic semiconductor layer; and a hydrophilic layer formed inthe opening of the hydrophobic layer, wherein the organic semiconductorlayer is formed on the hydrophilic layer.

According to another aspect of the present invention, there is provideda method of manufacturing a thin film transistor, the method including:forming a gate electrode on a substrate; forming an insulating layer tocover the gate electrode; forming source and drain electrodes on theinsulating layer; forming a hydrophobic layer to cover the source anddrain electrodes; forming an opening in the hydrophobic layer tocorrespond to an organic semiconductor layer to be formed; forming ahydrophilic layer on the opening of the hydrophobic layer; and formingthe organic semiconductor layer on the hydrophilic layer using anorganic semiconductor layer forming material.

According to another aspect of the present invention, there is provideda method of manufacturing a thin film transistor, the method including:forming a gate electrode on a substrate; forming an insulating layer tocover the gate electrode; forming a hydrophobic layer to cover theinsulating layer; forming an opening in the hydrophobic layer tocorrespond to an organic semiconductor layer to be formed; forming ahydrophobic layer in the opening of the hydrophilic layer; forming theorganic semiconductor layer on the hydrophilic layer using an organicsemiconductor layer forming material; and forming source and drainelectrodes.

According to another aspect of the present invention, there is provideda method of manufacturing a thin film transistor, the method including:forming source and drain electrodes on a substrate; forming ahydrophobic layer to cover the source and drain electrodes; forming anopening in the hydrophobic layer to correspond to an organicsemiconductor layer to be formed; forming an hydrophilic layer in theopening of the hydrophobic layer; forming the organic semiconductorlayer on the hydrophilic layer using an organic semiconductor layerforming material; forming an insulating layer to cover the organicsemiconductor layer and the source and drain electrodes; and forming agate electrode on the insulating layer.

According to another aspect of the present invention, there is provideda pixel of a flat panel display device that includes at least one thinfilm transistor and at least one light-emitting device electricallyconnected to the source or drain electrode of the thin film transistor.

According to another aspect of the present invention, there is provideda flat panel display device comprising a plurality of the pixels.

According to another aspect of the present invention, there is provideda method of forming a patterned layer of an organic semiconductormaterial on an underlying layer without etching the organicsemiconductor material, the method comprising: forming a hydrophobiclayer on the underlying layer; forming an opening in the hydrophobiclayer to define a patterned region; forming a hydrophilic layer in thepatterned region defined by the opening in the hydrophobic layer; andcontacting the hydrophilic layer with a organic semiconductor material,wherein the organic semiconductor material has a property of beingattracted to the hydrophilic layer and repelled by the hydrophobic layersuch that the patterned layer of organic semiconductor material isformed only on the hydrophilic layer.

The TFT includes the organic semiconductor layer that is spontaneouslyformed on a hydrophilic layer and that is not formed on a hydrophobiclayer. As a result, the organic semiconductor layer can be formed in adefined region by creating a hydrophilic layer in an opening of ahydrophobic layer, and additional patterning of the organicsemiconductor layer is not necessary. Therefore, a manufacturing costand manufacturing time of the TFT can be decreased. In addition, the TFThas improved electric properties.

Additional aspects and/or advantages of the invention will be set forthin part in the description which follows and, in part, will be obviousfrom the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will becomeapparent and more readily appreciated from the following description ofthe embodiments, taken in conjunction with the accompanying drawings ofwhich:

FIGS. 1 through 3 are sectional views illustrating structures of thinfilm transistors (TFTs) according to embodiments of the presentinvention

FIGS. 4A through 4G are sectional views illustrating sequentially amethod of manufacturing a TFT according to an embodiment of the presentinvention; and

FIGS. 5 and 6 are sectional views illustrating an organic light emittingdisplay device having a TFT according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

FIG. 1 is a sectional view of a thin film transistor (TFT) 10 accordingto an embodiment of the present invention. The TFT 10 includes asubstrate 11, a gate electrode 12, an insulating layer 13, source anddrain electrodes 14 a and 14 b, a hydrophobic layer 16, a hydrophiliclayer 17 and an organic semiconductor layer 15, which are sequentiallystacked upon one another.

The substrate 11 may be a glass, plastic, or metal substrate, forexample. The glass substrate may be formed of silicon oxide, siliconnitride, and the like. The plastic substrate may be formed of aninsulating organic compound. For example, the insulating organiccompound may be selected from the group consisting of polyethersulfone(PES), polyacrylate (PAR), polyetherimide (PEI), polyethylenenaphthalate (PEN), polyethyleneterephthalate (PET), polyphenylenesulfide (PPS), polyallylate, polyimide, polycarbonate (PC), celluloustriacetate (CAT), and cellulose acetate propionate (CAP), but is notlimited thereto. The metal substrate may include at least one selectedfrom the group consisting of carbon, iron, chrome, manganese, nickel,titanium, molybdenum, stainless steel (SUS), an Invar alloy, an Inconelalloy, and a Kovar alloy, but is not limited thereto. The metalsubstrate may be a metal foil. If a flexible substrate is desired,plastic or metal can be used.

A buffer layer, a barrier layer, or an impurities diffusion inhibitionlayer may be formed on one surface or both surfaces of the substrate 11.In particular, when the substrate 11 is a metal substrate, an insulatinglayer (not shown) may be further formed on the substrate 11.

The gate electrode 12 having a predetermined pattern is formed on thesubstrate 11. For example, the gate electrode 12 may be formed of ametal or a metal alloy, such as Au, Ag, Cu, Ni, Pt, Pd, Al, Mo, an Al:Ndalloy, an Mo:W alloy, etc. but the material of the gate electrode 12 isnot limited thereto.

The insulating layer 13 is formed on the gate electrode 12 to cover thegate electrode 12. The insulating layer 13 may be formed of an inorganiccompound, such as a metal oxide or a metal nitride, or an organiccompound, such as an insulting organic polymer, but the material of theinsulating layer 13 is not limited to thereto.

The source and drain electrodes 14 a and 14 b are formed on theinsulating layer 13. As shown in FIG. 1, the source and drain electrodes14 a and 14 b may overlap with a part of the gate electrode 12, but thestructure of the source and drain electrodes 14 a and 14 b is notlimited to thereto. Non-limiting examples of the material for the sourceand drain electrodes 14 a and 14 b include metals, such as Au, Pd, Pt,Ni, Rh, Ru, Ir, Os, Al and Mo, metal alloys of at least two metals, anAI:Nd alloy, an MoW alloy, metallic oxides, such as indium tin oxide(ITO), indium zinc oxide (IZO), NiO, Ag₂O, In₂O₃—Ag₂O, CuAlO₂, SrCu₂O₂,and Zr-doped ZnO. Combinations of two or more of the above-mentionedmetals or metallic oxides can be used.

The hydrophobic layer 16 and the hydrophilic layer 17 are formed on thesource and drain electrodes 14 a and 14 b to cover the source and drainelectrodes 14 a and 14 b or the insulating layer 13. The hydrophobiclayer 16 includes an opening defining a region corresponding to theorganic semiconductor layer 15 described later. The hydrophilic layer 17is formed in the opening. As used herein, the term “opening” may referto a region surrounded by a hydrophobic layer and where the hydrophobiclayer is not formed. The term “opening” may also refer to a region wherethe hydrophobic layer is removed after being formed or a region wherethe hydrophobic layer is altered to be a hydrophilic region. The organicsemiconductor layer 15 is formed after the hydrophobic layer 16 and thehydrophilic layer 17 are formed, and since a material of the organicsemiconductor layer 15 is generally hydrophilic, the organicsemiconductor layer can be formed only on the hydrophilic layer 17, evenwhen both the hydrophobic layer 16 and the hydrophobic layer 17 comeinto contact with the material that forms the organic semiconductorlayer 15. Therefore, the organic semiconductor layer 15 can be formedwithout additional patterning.

Throughout this specification, the term of “hydrophilic layer” is usedto indicate layer which is less hydrophobic than the “hydrophobiclayer.”

The hydrophobic layer 16 may include a group that allows a contact angleof water on the hydrophobic layer at least 90°, preferably, greater than90°, more preferably, in a range of greater than 90° and less than 180°.The hydrophilic layer 17 may include a group that allows a contact angleof water on the hydrophilic layer 10°-90°.

The term “contact angle” refers to the shape of a liquid droplet restingon a solid surface. With the assumption that there is a liquid on asolid plane in air, the term “contact angle” indicates the angle betweenthe tangent line of the liquid and the tangent line of the solid planeat a contact point of the liquid, the solid plane, and the air. Here, itcan be regarded that the solid plane adsorbs liquid vapor.

A contact angle may be used as a measure of wetting of a solid plane byliquid. For example, a small contact angle indicates a high degree ofwetting, i.e., a hydrophilic property and a high surface energy, and alarge contact angle indicates a low degree of wetting, i.e., ahydrophobic property and a low surface energy.

For measuring the contact angle, the following various methods may beused. These methods include a method of measuring a contact angle bydirectly projecting the shape of a liquid drop onto a screen, a methodof measuring the volume and height of a liquid droplet and the radius ofa lower circle to calculate a contact angle with the assumption that theliquid droplet is considered as a partial sphere, methods of measuring atilt angle and an adhesive tension of a solid plane in the state where acurved portion of a liquid droplet contacting the solid plane ispositioned to form a horizontal plane and the solid plane is positionedabove and perpendicular to the liquid droplet, etc. The above-describedexplanations of the contact angle and contact angle measurement methodsare apparent to those of ordinary skilled in the art.

The contact angles of the hydrophobic layer 16 and the hydrophilic layer17 may be measured, for example, using a contact angle method usingwater. The contact angle method using water may be a method of measuringthe angle between the surface of layer and a water droplet using a CCDwhile supplying water in microliter amounts at a room temperature.

The material of the hydrophobic layer 16 may include a C₃-C₃₀alkylgroup; a C₃-C₃₀ alkyl group substituted with one or more halogen atoms,and the like, but the material is not limited thereto.

More particularly, the hydrophobic layer 16 may include a unit havingformula (1) below or a repeating unit of formula (2) below:

In formulas (1) and (2), R1, R2 and R3 are each selected from a halogenatom; a C3-C30 alkyl group; and a C3-C30 alkyl group substituted by atleast one halogen atom, wherein at least one of R1, R2 and R3 may be aC3-C30 alkyl group; or a C3-C30 alkyl group substituted by at least onehalogen atom. For example, R1, R2 and R3 may be each selected from ahalogen atom; a C3-C20 alkyl group; and a C3-C20 alkyl group substitutedby at least one halogen atom, wherein at least one of R1, R2 and R3 maybe a C3-C20 alkyl group or a C3-C20 alkyl group substituted by at leastone halogen atom.

In formulas (1) and (2), R4 may be a C3-C30 alkyl group; or a C3-C30alkyl group substituted by at least one halogen atom. For example, R4may be a C3-C20 alkyl group; or a C3-C20 alkyl group substituted by atleast one halogen atom.

In formulas (1) and (2), * indicates binding with the source and drainelectrodes 14 a and 14 b or the insulating layer 13.

In particular, the repeating unit having formula (2) may be obtained asa result of hydrolysis when a material having an alkoxy group is used asa starting material for the hydrophobic layer 16.

In a TFT according to an embodiment of the present invention, thehydrophobic layer 16 may include a unit having formula (3) or (4), butthe unit is not limited thereto;

In formulas (3) and (4), * indicates binding with the source and drainelectrodes 14 a and 14 b or the insulating layer 13.

Examples of a material of the hydrophilic layer 17 may include a C5-C30aryl group, a C3-C30 heteroaryl group, a C6-C30 aralkyl group, a C4-C30heteroaralkyl group and the like, but are not limited thereto.

More particularly, the hydrophilic layer 17 may include a unit havingformula (5) below or a repeating unit having formula (6) below:

In formulas (5) and (6), Q1, Q2 and Q3 are each selected from the groupconsisting of a halogen atom, a C5-C30 aryl group, a C3-C30 heteroarylgroup, a C6-C30 aralkyl group and a C4-C30 heteroaralkyl group, whereinat least one of Q1, Q2 and Q3 may be a C5-C30 aryl group, a C3-C30heteroaryl group, a C6-C30 aralkyl group, or a C4-C30 heteroaralkylgroup.

In formulas (5) and (6), Q4 may be a C5-C30 aryl group, a C3-C30heteroaryl group C6-C30 aralkyl group or a C4-C30 heteroaralkyl group.

In formulas (5) and (6), *′ indicates binding with the source and drainelectrodes 14 a and 14 b or the insulating layer 13.

In the TFT according to an embodiment of the present invention, thehydrophilic layer 17 may include a unit having formula (7) or (8) below,but the unit is not limited thereto;

In formulas (7) and (8), *′ indicates binding with the source and drainelectrodes 14 a and 14 b or the insulating layer 13.

Throughout this specification, where an aryl group, a heteroaryl group,an aralkyl group or a heteroaralkyl group are mentioned, it is to beunderstood that such groups may include at least two carbocyclic ringsor heterocyclic rings, which may be attached together or may be fused.

Throughout this specification, a term “aralkyl group” refers to anaryl-substituted alkyl radical.

Throughout the specification, where a heteroaryl group or a heteroararylgroup are mentioned, it is to be understood that such groups may includeat least one hetero atom selected from the group consisting of N, O, Pand S.

The aryl group, heteroaryl group, aralkyl group or heteroaralkyl groupmay be each substituted by at least one selected from the groupconsisting of a halogen atom, a cyano group and a hydroxyl group.

The organic semiconductor layer 15 is formed on the hydrophilic layer17. When the organic semiconductor layer 15 is formed, the organicsemiconductor layer 15 is spontaneously formed only on the hydrophiliclayer 17 even when both the hydrophobic layer 16 and the hydrophiliclayer 17 come into contact with the material of the organicsemiconductor layer 15. This is because the material of the organicsemiconductor layer 15 is generally hydrophilic and is thereforeattracted to the hydrophilic layer and repelled by the hydrophobiclayer. Therefore, an additional patterning process to form the organicsemiconductor layer 15 of the TFT according to an aspect of the presentinvention is unnecessary.

Examples of an organic semiconductor material for the organicsemiconductor layer 15 include pentacene, tetracene, anthracene,naphthalene, α-6-thiophen, α-4-thiophen, perylene and a derivativethereof, rubrene and a derivative thereof, coronene and a derivativethereof, perylene tetracarboxylic diimide and a derivative thereof,perylene tetracarboxylic dianhydride and a derivative thereof,polythiophene and a derivative thereof, polyparaphenylene vinylene and aderivative thereof, polyparaphenylene and a derivative thereof,polyfluorene and a derivative thereof, polythiophene vinylene and aderivative thereof, a polythiophene-heterocyclic aromatic copolymer anda derivative thereof, an oligonaphthalene and a derivative thereof, anoligothiophene of α-5-thiophene and a derivative thereof, ametal-containing or metal-free phthalocyanine and a derivative thereof,pyromellitic dianhydride and a derivative thereof, pyromellitic diimideand a derivative thereof, or the like. Combinations of two or more ofthese materials can be used.

FIG. 2 is a sectional view of TFT 10′ according to another embodiment ofthe present invention. The TFT 10′ includes a substrate 11, a gateelectrode 12, insulating layer 13, a hydrophobic layer 16, a hydrophiliclayer 17, an organic semiconductor layer 15 and source and drainelectrodes 14 a and 14 b, which are sequentially stacked upon oneanother.

FIG. 3 is a sectional view of TFT 10″ according to another embodiment ofthe present invention. The TFT 10″ includes a substrate 11, source anddrain electrodes 14 a and 14 b, a hydrophobic layer 16, a hydrophiliclayer 17, an organic semiconductor layer 15, an insulating layer 13 andgate electrode 12, which are sequentially stacked upon one another. Thematerials that make up the substrate 11, gate electrode 12, insulatinglayer 13, hydrophobic layer 16, hydrophilic layer 17, organicsemiconductor layer 15 and source and drain electrodes 14 a and 14 b inTFTs 10′ and 10″ shown in FIGS. 2 and 3 have the same composition as theequivalent structures in the TFT 10 of FIG. 1, and thus a detaileddescription of the TFTs 10′ and 10″ will be omitted.

A TFT according to aspects of the present invention may be formed usingvarious methods. For example, a method of manufacturing a TFT accordingto the embodiment of the FIG. 1 may include: forming a gate electrode ona substrate; forming an insulating layer to cover the gate electrode;forming source and drain electrodes on the insulating layer; forming ahydrophobic layer to cover the source and drain electrodes; forming anopening in the hydrophobic layer to define a region in which an organicsemiconductor layer is to be formed; forming a hydrophobic layer in theopening of the hydrophobic layer; and forming the organic semiconductorlayer on the hydrophilic layer by providing an organic semiconductorlayer forming material.

A method of manufacturing a TFT according to the embodiment of FIG. 2may include: forming a gate electrode on a substrate; forming aninsulating layer to cover the gate electrode; forming a hydrophobiclayer to cover the insulating layer; forming an opening in thehydrophobic layer to define a region in which an organic semiconductorlayer is to be formed; forming a hydrophilic layer in the opening of thehydrophobic layer; forming an organic semiconductor layer on thehydrophilic layer by providing an organic semiconductor layer formingmaterial; and forming source and drain electrodes.

A method of manufacturing a TFT according to the embodiment of FIG. 3may include: forming source and drain electrodes on a substrate; forminga hydrophobic layer to cover the source and drain electrodes; forming anopening in the hydrophobic layer to define a region in which an organicsemiconductor layer is to be formed; forming an hydrophilic layer in theopening of the hydrophobic layer; forming the organic semiconductorlayer on the hydrophilic layer by providing an organic semiconductorlayer forming material; forming an insulating layer to cover the organicsemiconductor layer and the source and drain electrodes; and forming agate electrode on the insulating layer.

The method of manufacturing a TFT may be more generally described asincluding: forming a gate electrode; forming an insulating layer;forming source and drain electrodes; forming a hydrophobic layer;forming an opening in the hydrophobic layer to define a regioncorresponding to an organic semiconductor layer to be formed; forming ahydrophilic layer in the region of the hydrophobic layer defined by theopening; and forming the organic semiconductor layer on the hydrophiliclayer. In this description, only the relative order in which thehydrophobic layer, hydrophilic layer and organic semiconductor layer areformed is specified. That is, the hydrophobic layer must be formedbefore an opening can be provided in the hydrophobic layer and beforethe hydrophilic layer can be formed in the opening. The hydrophiliclayer must be formed before the organic semiconductor layer is formed onthe hydrophilic layer. It is to be understood that the remaining layersmay be formed in any order on a substrate that provides a thin filmtransistor. For example, the layers may be formed in any order thatprovides a TFT of the embodiments shown in FIG. 1, FIG. 2 or FIG. 3.

When the source and drain electrodes include an oxidizable metal, theforming the source and drain electrodes may further include oxidizingsurfaces of the source and drain electrodes. This operation is performedin order to increase the adhesive force between the source/drainelectrodes and hydrophobic layer and/or hydrophilic layer which will beformed later.

The oxidizing the surfaces of the source and drain electrodes can beimplemented using various methods. For example, a method of annealingthe surfaces of the source and drain electrodes in an atmosphericcondition such as, for example, in an oxygen atmosphere, a method oftreating the surfaces of the source and drain electrodes with a gas suchas, for example, oxygen plasma, a method of chemically treating thesurfaces of the source and drain electrodes with an oxidant, forexample, hydrogen peroxide, or other methods can be used. However, themethods that can be used to oxidize the surfaces of the source and drainelectrodes are not limited thereto.

The forming of the hydrophobic layer or the hydrophilic layer may beperformed using a deposition method; a coating method, such as, forexample, spin coating, deep coating, micro contact printing, inkjetprinting, etc.; or a self-assembled monolayer manufacturing method, butis not limited to these. These methods are known to those of ordinaryskill in the art. In the self-assembled monolayer manufacturing method,a catalyst may be further used to facilitate a reaction, such ashydrolysis, condensation, etc., involved in forming the hydrophobiclayer or the hydrophilic layer.

The hydrophobic layer may include a group leading to a contact angle ofwater on the hydrophobic layer of at least 90°, such as, for example,greater than 90°, or more specifically, in a range of greater than 90°and less than 180°. Examples of the hydrophobic layer include a C3-C30alkyl group; and a halogen atom-substituted C3-C30 alkyl group, but arenot limited thereto.

The hydrophilic layer may include a group which allows a contact angleof water on the hydrophilic layer 10°-90°. Examples of groups that maybe included in the hydrophilic layer include a C5-C30 aryl group, aC3-C30 heteroaryl group, a C6-C30 aralkyl group, and a C4-C30heteroaralkyl group, but are not limited thereto.

More particularly, the hydrophobic layer may be formed by using acompound having formula (9) below as a reactant in forming thehydrophobic layer:

In formula (9), R₅, R₆ and R₇ are each selected from a halogen atom; aC₁-C₁₀ alkoxy group; a C₃-C₃₀alkyl group; or a C₃-C₃₀alkyl groupsubstituted by a halogen atom wherein at least one of R₅, R₆ and R₇ maybe a C₃-C₃₀ alkyl group; or a C₃-C₃₀ alkyl group substituted by ahalogen atom.

R₈ is halogen atom or a C₁-C₁₀ alkoxy group.

For example, depending on the selection of R₅, R₆ and R₇, the compoundof formula (9) may react directly with the source and drain electrodes14 a and 14 b and/or the insulating layer 13 to form the unit of formula(1) or may react with itself as well as with the source and drainelectrodes 14 a and 14 b or the insulating layer 13 to form therepeating unit of formula (2).

In a method of manufacturing a TFT according to an embodiment of thepresent invention, the hydrophobic layer 16 may be formed using acompound having formula (10) or (11) below. However, the method is notlimited to these compounds.

For example, a compound having formula (10) or (11) may react with thesource and drain electrodes 14 a and 14 b and/or the insulating layer 13to form a unit of formula (3) or (4), respectively.

The hydrophilic layer may be formed using a compound having formula (12)below as a reactant in forming the hydrophilic layer:

In formula (12), Q5, Q6 and Q7 are each selected from a halogen atom, aC1-C10 alkoxy group, a C5-C30aryl group, a C3-C30 heteroaryl group, aC6-C30 aralkyl group or a C4-C30 heteroaralkyl group, wherein at leastone of Q5, Q6 and Q7 is a C5-C30 aryl group, a C3-C30 heteroaryl group,a C6-C30 aralkyl group or a C4-C30 heteroaralkyl group, and Q8 is ahalogen atom or a C1-C10 alkoxy group.

For example, depending on the selection of Q₅, Q₆ and Q₇, the compoundof formula (12) may react directly with the source and drain electrodes14 a and 14 b and/or the insulating layer 13 in the region from whichthe hydrophobic layer has been removed to form the unit of formula (5)or may react with itself as well as with the source and drain electrodes14 a and 14 b or the insulating layer 13 in the region from which thehydrophobic layer has been removed to form the repeating unit of formula(6)

In a method of manufacturing a TFT according to an embodiment of thepresent invention, the hydrophilic layer may be formed using a compoundhaving formula (13) or (14) below:

For example, a compound having formula (13) or (14) may react with thesource and drain electrodes 14 a and 14 b and/or the insulating layer 13in the region from which the hydrophobic layer has been removed to forma unit of formula (7) or (8), respectively.

In the methods of manufacturing TFTs according to aspects of the presentinvention, the forming of an opening that defines a region correspondingto the organic semiconductor layer 15 in the hydrophilic layer 17 may beperformed using various known methods. For example, laser ablationtechnology (LAT) may be used to remove the hydrophobic layer in theregion where the organic semiconductor layer is to be formed. An openinghaving at least about 5 μm in width can be formed using laser ablation,which is suitable to form a precise opening. Accordingly, an organicsemiconductor layer having a very precise pattern can be obtained usinglaser ablation.

Hereinafter, a method of manufacturing a TFT according to an embodimentof the present invention will be described with reference to FIGS. 4Athrough 4G.

A gate electrode 42 is formed on a substrate 41 as shown in FIG. 4A, andan insulating layer 43 is formed to cover the gate electrode 42 as shownin FIG. 4B. Next, source and drain electrodes 44 a and 44 b having apredetermined pattern are formed on the insulating layer 43. Next, ahydrophobic layer 46 is formed to cover the source and drain electrodes44 a and 44 b and the insulating layer 43.

The hydrophobic layer 46 may be formed using a deposition method; acoating method, such as, for example, spin coating, dip coating, microcontact printing, inkjet printing, etc.; or a self-assembled monolayermanufacturing method, all of which are known to those of skill in theart. For example, a compound that attaches to the source and drainelectrodes 44 a and 44 b and the insulating layer 43 may be applied.

Next, an opening 46 a is formed in the hydrophobic layer 46 as shown inFIG. 4E by etching to define a region in which an organic semiconductorlayer is to be formed. Here, various known etching methods may be used.For example, laser ablation, etc. can be used. As shown in FIG. 4E, theetching exposes the underlying insulating layer 43 and source and drainelectrodes 44 a and 44 b in the region of the opening. Next, ahydrophilic layer 47 is formed in the opening 46 a of the hydrophobiclayer 46 as shown in FIG. 4F. In particular, the hydrophilic layer 47 isformed on the portions of the insulating layer 37 and source and drainelectrodes 44 a and 44 b that were exposed by the etching. Thehydrophilic layer 47 may be formed using a known method such as, adeposition method; a coating method, such as, for example, spin coating,dip coating, micro contact printing, inkjet printing, etc.; or aself-assembled monolayer manufacturing method, all of which are known tothose of skill in the art.

Next, the organic semiconductor layer 45 is formed on the hydrophiliclayer 47 as shown in FIG. 4G by providing an organic semiconductor layerforming material. Since the organic semiconductor forming material istypically a hydrophilic material, the organic semiconductor formingmaterial is attracted to the hydrophilic layer 47 and repelled by thehydrophobic layer 46. Thereby, the organic semiconductor layer can beformed only on the hydrophilic layer 47 even when both the hydrophobiclayer 46 and the hydrophobic layer 47 come into contact with thematerial that forms the organic semiconductor layer 45. Therefore, anadditional patterning process is unnecessary to form the organicsemiconductor layer 45 in the desired location.

The method described herein provides a TFT having the same structure asthe TFT shown in FIG. 1. Although different reference numerals are used,it is to be understood that the substrate 41, gate electrode 42,insulating layer 43, hydrophobic layer 46, hydrophilic layer 47, organicsemiconductor layer 45 and source and drain electrodes 44 a and 44 bdescribed in the method have the same composition as the equivalentstructures in the TFT 10 of FIG. 1 as described above.

As would be apparent to persons skilled in the art, the TFTs 10′ and 10″shown in FIGS. 2 and 3 can be manufactured by changing the order inwhich the various layers are deposited.

A TFT having the above-mentioned structure may be included in a flatpanel display, such as a liquid crystalline display (LCD), an organiclight-emitting display, etc.

FIG. 5 is a sectional view of an organic light-emitting displayaccording to an embodiment of the present invention as a flat paneldisplay including a TFT 20 according to an aspect of the presentinvention.

FIG. 5 illustrates a single sub-pixel of an organic light-emittingdisplay. Typically, each sub-pixel of an organic light-emitting displayincludes an organic light-emitting device (OLED) 30 as a self-luminouselement and at least one TFT.

The organic light-emitting display may include various pixel patterns,such as, for example, red, green, and blue pixels, according to aluminescent color of the organic light-emitting device.

Referring to FIG. 5, a gate electrode 22 having a predetermined patternis formed on a substrate 21, and an insulating layer 23 is formed tocover the gate electrode 22. Source and drain electrodes 24 a and 24 bare formed on the insulating layer 23. A hydrophobic layer 26 and ahydrophilic layer 27 are formed on the source and drain electrodes 24 aand 24 b. An organic semiconductor layer 25 is formed on the hydrophiliclayer 27. Each layer included in the TFT 20 is equivalent to thecorresponding layers in the TFT of FIG. 1, and thus a detaileddescription of each layer will be omitted.

After the organic semiconductor layer 25 is formed, a passivation layer28 is formed to cover the TFT 20. The passivation layer 28 is formed asa single-layered or multi-layered structure, and may be formed of anorganic material, an inorganic material or an organic/inorganiccomposite material.

A pixel defining layer 29, which defines a pixel, is formed on thepassivation layer 28. A pixel electrode 31 is formed on the pixeldefining layer 29 and a portion of the pixel electrode extends throughthe pixel defining layer 29 to connect with one of the source and drainelectrodes 24 a and 24 b. An organic layer 32 of the OLED 30 is formedon a pixel electrode 31.

An organic light emitting display device made up of a plurality oforganic light emitting devices 30 displays predetermined imageinformation by emitting light of red, green and blue color according tothe flow of current. The organic light emitting device 30 includes thepixel electrode 31 connected to one of the source and drain electrodes24 a and 24 b, a facing electrode 33 covering the entire pixel, and theorganic layer 32 interposed between the pixel electrode 31 and thefacing electrode 33. The present invention is not limited to thisstructure, and the OLED 30 can have various structures.

The organic layer 32 may be a small-molecular weight organic layer or apolymer organic layer. When the organic layer 32 is a small-molecularweight organic layer, the organic layer 32 may have a structureincluding one of a hole injection layer (HIL), a hole transport layer(HTL), an emission layer (EML), an electron transport layer (ETL), andan electron injection layer (EIL) or combinations of these layers.Examples of organic materials for the small-molecular weight organiclayer include copper phthalocyanine (CuPc),N,N-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB),tris-8-hydroxyquinoline aluminum (Alq3), etc. The small-molecular weightorganic layer can be formed using a deposition method such as, forexample, vacuum deposition.

When the organic layer 32 is a polymer organic layer, the organic layer32 may have a structure including an HTL and an EML. The HTL may beformed of poly-3,4-ethylenedioxythiophene (PEDOT), and the EML may beformed of a poly-phenylenevinylene (PPV)-based or polyfluorene-basedpolymer material using screen printing, inkjet printing, etc.

The organic layer 32 is not limited to the above-described organiclayers, and may have various structures.

The pixel electrode 31 may act as an anode, and the facing electrode 33may act as a cathode. Alternatively, the polarities of the pixelelectrode 31 and the facing electrode 33 may be reversed. That is, thepixel electrode 31 may act as a cathode, and the facing electrode 33 mayact as an anode.

FIG. 6 is a sectional view illustrating a flat panel display accordingto another embodiment of the present invention. The flat panel displayof FIG. 6 is the same as the flat panel display of FIG. 5 except thatthe TFT as shown in FIG. 3 is used.

A TFT according to an aspect of the present invention may also be usedin a liquid crystal display (LCD). Unlike a method of manufacturing anorganic light-emitting display, a method of manufacturing an LCD furtherincludes forming a lower substrate by forming a lower alignment layer(not shown) covering the pixel electrode 31.

A TFT according to aspects of the present invention can be installed ineach sub-pixel as illustrated in FIG. 5, or in a driver circuit (notshown) where no image is formed.

The present embodiments will be described in further detail withreference to the following example.

EXAMPLE

A substrate including a gate electrode formed of MoW (100-nm thick), aninsulating layer formed of SiO₂ (200-nm thick), and source and drainelectrodes formed of ITO (100-nm thick) was prepared. The substrate wassoaked in an octadecyl trichlorosilane solution (50 mM anhydroustoluene) for three hours. The substrate was washed with toluene,acetone, and then isopropanol, and dried at 120° for an hour and curedto form a hydrophobic layer to cover the source and drain electrodes andthe insulating layer. The hydrophobic layer included a unit havingformula (3).

Next, a region corresponding to the organic semiconductor layer, wasexposed by etching the hydrophobic layer using a KrF excimer laser as alaser ablation apparatus. In the etching, hydroxyl groups present on thesurface of the insulating layer and source and drain electrodes wereexposed and then were allowed to react with a hydrophilic layer formingmaterial when coming into contact with the same, thereby forming ahydrophilic layer in the region etched from the hydrophobic layer.

The resulting substrate was soaked in a phenyl trichlorosilane solution(50 mM anhydride toluene), as a hydrophilic layer forming material, forthree hours. The substrate was washed sequentially with toluene, acetoneand isopropanol, and dried and cured at 120° for an hour. Thehydrophilic layer including a unit having formula (7) was formed in theregion defined by the opening of the hydrophobic layer.

Next, pentacene was deposited onto the substrate was such that theorganic semiconductor layer (70 nm) was formed only on the hydrophiliclayer, thereby resulting in an organic TFT being according to an aspectof the present invention.

As described above, in a TFT according to aspects of the presentinvention, because the hydrophobic layer and the hydrophilic layer areformed before forming the organic semiconductor layer, the organicsemiconductor layer can be subsequently formed only on the hydrophiliclayer without an additional etching process. Therefore, themanufacturing cost and time of the TFT can be decreased, and theelectric properties of the TFT can be improved. Thus, a flat paneldisplay with improved reliability can be realized using the TFT.

Although a few embodiments of the present invention have been shown anddescribed, it would be appreciated by those skilled in the art thatchanges may be made in this embodiment without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A method of manufacturing a thin film transistor, the methodcomprising: forming a gate electrode; forming an insulating layer;forming source and drain electrodes; forming a hydrophobic layer;forming an opening in the hydrophobic layer to define a regioncorresponding to an organic semiconductor layer to be formed, whereinthe opening exposes a portion of the source and drain electrodes and aportion of the insulating layer between the source and drain electrodes;forming a hydrophilic layer in the region of the hydrophobic layerdefined by the opening by depositing a hydrophilic layer formingmaterial in the region such that the hydrophilic layer covers theexposed portion of the source and drain electrodes and the exposedportion of the insulating layer between the source and drain electrodes;and forming the organic semiconductor layer on the hydrophilic layer,wherein the organic semiconductor layer is formed of an organicsemiconductor material that has a property of being attracted to thehydrophilic layer and repelled by the hydrophobic layer such that apatterned layer of organic semiconductor material is formed only on thehydrophilic layer and such that the formed organic semiconductor layeroverlaps the portions of the source and drain electrodes and the portionof the insulating layer between the source and drain electrodes thatwere exposed by the opening and were covered by the hydrophilic layer.2. The method of claim 1, wherein the hydrophobic layer includes a groupwhich allows a contact angle of water on the hydrophobic layer of atleast 90°.
 3. The method of claim 1, wherein the hydrophilic layerincludes a group which allows a contact angle of water on thehydrophilic layer of 10°-90°.
 4. The method of claim 1, wherein thehydrophobic layer is formed using a compound having formula (9) below:

where R₅, R₅ and R₇ are each selected from the group consisting of ahalogen atom, a C₁-C₁₀ alkoxy group, a C₃-C₃₀ alkyl group and a C₃-C₃₀alkyl group substituted by at least one halogen atom, wherein at leastone of R₅, R₆ and R₇ are a C₃-C₃₀ alkyl group or a C₃-C₃₀ alkyl groupsubstituted by at least one halogen atom; and R₈ is a halogen atom orC₁-C₁₀ alkoxy group.
 5. The method of claim 4, wherein the hydrophobiclayer is formed using a compound having formula (10) or (11) below:


6. The method of claim 1, wherein the hydrophilic layer is formed usinga compound having formula (12) below:

wherein, Q₅, Q₆ and Q₇ are each selected from the groups consisting of ahalogen atom, a C₁-C₁₀ alkoxy group, a C₅-C₃₀ aryl group, a C₃-C₃₀heteroaryl group, a C₆-C₃₀ aralkyl group or a C₄-C₃₀heteroaralkyl group,wherein at least one of Q₅, Q₆ and Q₇ is a C₅-C₃₀ aryl group, a C₃-C₃₀heteroaryl group, a C₆-C₃₀ aralkyl group and a C₄-C₃₀heteroaralkylgroup, and Q₈ is a halogen atom or a C₁-C₁₀ alkoxy group.
 7. The methodof claim 6, wherein the hydrophilic layer is formed using a compoundhaving formula (13) or (14) below:


8. The method of claim 1, wherein the opening in the hydrophobic layeris formed by laser ablation.
 9. The method of claim 1, wherein theorganic semiconductor layer is formed by contacting the hydrophiliclayer with a hydrophilic organic semiconductor forming material suchthat the organic semiconductor forming material is attracted to thehydrophilic layer and repelled by the hydrophobic layer.
 10. The methodof claim 1, wherein an entire exposed surface of the region defined bythe opening is covered with the hydrophilic layer.
 11. The method ofclaim 1, wherein in the forming of the hydrophobic layer, an entiresurface of the source and drain electrodes is covered with thehydrophobic layer.
 12. A method of forming a patterned layer of anorganic semiconductor material on an underlying layer including sourceand drain electrodes without etching the organic semiconductor material,the method comprising: forming a hydrophobic layer on the underlyinglayer; forming an opening in the hydrophobic layer to define a patternedregion; forming a hydrophilic layer in the patterned region defined bythe opening in the hydrophobic layer by depositing a hydrophilic layerforming material in the patterned region; and contacting the hydrophiliclayer with a organic semiconductor material, wherein the organicsemiconductor material has a property of being attracted to thehydrophilic layer and repelled by the hydrophobic layer such that thepatterned layer of organic semiconductor material is formed only on thehydrophilic layer, and wherein the patterned region defined by theopening in the hydrophobic layer exposes a portion of the source anddrain electrodes such that the formed hydrophilic layer covers theportion of the source and drain electrodes exposed by the forming of theopening and such that the patterned layer of organic semiconductormaterial formed only on the hydrophilic layer overlaps the portion ofsource and drain electrodes.
 13. The method of claim 12, wherein anentire exposed surface of the patterned region defined by the opening iscovered with the hydrophilic layer.
 14. The method of claim 12, whereinin the forming of hydrophobic layer an entire surface of the source anddrain electrodes is covered with the hydrophobic layer.